A hydrogenated ring-opening polymer of a norbornene-based monomer such as dicyclopentadiene is a type of so-called cycloolefin polymer that exhibits excellent transparency, low birefringence, forming processability and the like, and thus is used as a material that can be applied to various applications such as optical applications.
A hydrogenated ring-opening polymer of dicyclopentadiene is normally obtained in the form of an amorphous polymer that has an atactic structure. However, the amorphous hydrogenated ring-opening polymer of dicyclopentadiene having the atactic structure may exhibit insufficient heat resistance, mechanical strength, solvent resistance and the like depending on the application. Hence, in order to improve the performance of such a hydrogenated ring-opening polymer, a hydrogenated ring-opening polymer of dicyclopentadiene that has crystallinity obtained by producing a hydrogenated ring-opening polymer of dicyclopentadiene having a tactic structure on its main chain has been proposed.
For example, Patent Literature 1 discloses that a dicyclopentadiene ring-opening polymer having cis-syndio regularity that is soluble in a hydrocarbon solvent such as a cyclohexane at room temperature is obtained by subjecting dicyclopentadiene to ring-opening polymerization using a polymerization catalyst that mainly includes a group 6 transition metal compound having a specific substituent such as a phenylimidotungsten tetrachloride diethyl ether complex, and furthermore a hydrogenated syndiotactic crystalline dicyclopentadiene ring-opening polymer having crystallinity is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer using a mixture of a bis(tricyclohexylphosphine)benzylideneruthenium(IV) dichloride and ethyl vinyl ether or the like, as a hydrogenation catalyst. In addition, Patent Literature 2 discloses that a crystalline dicyclopentadiene ring-opening polymer having cis-iso regularity that is insoluble in a hydrocarbon solvent such as cyclohexane at room temperature is obtained by subjecting dicyclopentadiene to ring-opening polymerization using a polymerization catalyst that mainly includes a group 4 to 6 transition metal compounds that include a specific aromatic dioxy group as a ligand such as a phenylimidotungsten bisphenolate complex, and a hydrogenated isotactic crystalline dicyclopentadiene ring-opening polymer having crystallinity is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer using RuHCl(CO) (PPh3)2 or the like as a hydrogenation catalyst.